I take the blame for that one. I added the hook because, if a process
were to die whilst holding one or more grants, there were no hooks that
would make it possible to carry out the grant-unmap. All existing hooks
on either the device or the VMA were called *after* the PTEs were cleared.
It gets better, though. The same hook is used in the version of blktap
in linux-2.6.18-xen (not, as far as I can see, in the sparse tree for
xen-3.1-testing):
http://xenbits.xensource.com/linux-2.6.18-xen.hg?file/fd879c0688bf/drivers/xen/blktap/blktap.c
Reverting back to the old (hookless) behaviour would be a retrograde
step IMHO.
Cheers,
Derek Murray.
Gerd Hoffmann wrote:
Stephen C. Tweedie wrote:
Hi all,
driver domains
Looked at the gntdev (grant table mappings for user space) driver,
noticed that one is not self-contained. It needs a hook for page unmapping:
http://xenbits.xensource.com/xen-3.1-testing.hg?rev/7180d2e61f92
plus an s/ptep_get_and_clear_full/zap_pte/ fixup a few changesets
later.
Upstreaming that one could become *uhm* intresting. Nevertheless the
gntdev functionality is quite useful for writing pure userspace
backend drivers ...
cheers,
Gerd
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